In recent years, in order to realize magnetic disks of higher recording density (track density), techniques for magnetically writing/reading information while heat-assisting with a laser beam (heat-assisted write/read system) have been developed. The magnetic recording media for writing and reading by the foregoing heat-assisted read/write system and the writing/reading method based on the heat-assisted read/write system are disclosed, for example, in Journal of Magnetics Society of Japan Vol. 23 Supplement, No. S1(1999), pp. 233-236 or an Journal of Magnetics Society of Japan “Vol. 23, No. 8, 1999, pp. 1901-1906”.
FIG. 12 is a cross-sectional view of an information writing/reading device, which explains the writing/reading method by the heat-assisted read/write system. As illustrated in FIG. 12, a light beam 102 emitted from an optical head 101 is projected onto a magnetic recording medium 104 formed on a disk substrate 103. In this writing/reading method, the light beam 102 projected onto the recording medium 104 is used in performing a tracking control and raising the temperature of the recording medium 104. The information writing/reading device is structured such that a magnetic head 105 is provided opposing the optical head 101 via the disk substrate 103 and the recording medium 104. The information writing/reading device performs a writing/reading operation with respect to an area (high temperature area) irradiated with the light beam 102.
FIG. 13 is a plan view of the information writing/reading device of FIG. 12. When writing, a light beam of a high intensity is projected onto the recording medium 104 so as to heat the recording medium 104 to a writing temperature. In the portion of the high temperature area 106 (area heated to or above the writing temperature) of the recording medium 104, where a writing magnetic field is applied from the magnetic head 105, the magnetization direction is reversed according to the information, and the information are digitally written based on the magnetization direction. In the foregoing structure, by scanning the light beam 102 and the magnetic head 105 at the same time in a direction of an arrow shown in FIG. 13, recording marks 107 are sequentially written on recording tracks of the recording medium 104.
On the other hand, when a reading operation is performed in the information writing/reading device, a light beam 102 of a lower intensity than that of the light beam 102 used when writing is projected on the recording medium 104 so as to heat the portion irradiated with the light beam of the recording medium 104 to a reading temperature. Then, the magnetic field generated from the recording marks 107 in the portion of the high temperature area 106 (an area heated to or above a reading temperature) covered with the magnetic head 105 is read out from the magnetic head 105, thereby reading written information. As described, by scanning the light beam 102 and the magnetic head 105 at the same time in a direction of the arrow shown in the Figure, it is possible to sequentially read information written in each recording mark 107.
However, the foregoing conventional structure has a limit in increasing the density of the recording track. Specifically, in the information writing/reading device of FIG. 13, the linear density of the recording marks 107 formed along the recording tracks is determined by a width of a magnetic gap of the magnetic head 105, and in this structure, writing and reading operations can be performed with respect to the recording marks 107 formed at intervals of not more than 0.5 μm.
On the other hand, in the foregoing conventional information writing/reading device, in the direction orthogonal to the direction of the recording tracks, the width of each recording mark 107 (the length in the direction orthogonal to the recording track) which is defined by a spot diameter of the light beam 102 is around 1 μm at the minimum due to the diffraction limit of the light beam 102, which hinders an increase in the density of the recording tracks formed on the recording medium 104.